Self-hardening compound, particularly for dental-medical application

ABSTRACT

Dental cements contain zinc oxide and an aqueous solution of a polymer of an unsaturated alpha, beta-dicarboxylic acid.

Unlted States Patent [1 1 u 11 3,882,080 Schmitt et al. May 6, 1975 SELF-HARDENING COMPOUND, {52] US. Cl 260/4229; 32/15; 260/29.6 M; PARTICULARLY FOR DENTAL-MEDICAL 260/4243; 52; 260/784 R; 260/874; APPLICATION 260/90]; 260/998] 1 t [5 l] Int. Cl. .t C08f 45/04 [75] Inventors. Werner SchmItt, Robert Purrmann, [58] Field of Search llllll U 260/784 R 4243 998] 1. both of Stamberg; Peter Jochum; 260/42 29 42 52 874 gm Wolf-Dieter Zahler, both at Hechendorf, all of Germany [56] References cued [73] Assignee: Espe Fabrik Pharmazeutischer UNITED STATES PATENTS Preparate GmbH, Seefeld, Oberbay, 3,655.605 4/1972 Smith et ul 260/998,] l Germany 3 804 794 4/1974 Schmitt et ai 106/35 [22] Filed: Feb. 26, 1974 Primary ExaminerJames H. Derrmglon 1 PP N05 445,827 Attorney, Agent. or Firm-Ostr0lenk, Faber. Gerb &

Related US. Application Data Soffen [63] Continuation-impart 0i" Ser No. 215,]39. Jan, 3.

1972, Pat No. 3,804,794 [57] ABSTRACT Dental cements contain zinc oxide and an aqueous s0- 30 Foreign Appficamm priority Dam lution of a polymer of an unsaturated alpha, beta- Jan. 15,197! Germany 2l0l939 dicarboxylic acid.

7 Claims, N0 Drawings SELF-HARDENING COMPOUND. PARTICULARLY FOR DENTAL-MEDICAL APPLICATION This is a continuation-in-part of application Ser. No. 2l5,l39 filed Jan. 3. 1972 and now US. Pat. No. 3,804,794.

BACKGROUND OF THE INVENTION The cements used in dentistry, which serve to strengthen dental prothesis parts and to produce underfillings and to close root canals, are divided substantially into three groups. namely:

1. Phosphate cements (see eg. "Materials for the Practicing Dentist." p. 34-37. The CV. Mosby Co. St. Louis, 1969).

2. Zinc oxide-eugemoi-preparations (lbid p. 44-48).

3. Polycarboxylate cements DOS 1.617.688).

The essential properties of the polycarboxylate Cemcnts. also compared to the other two types of cement. have been complied by H. Durner in Das Deutsche Zahnaerzteblatt vol. 23. no. l2/l969, p.583-586.

In a brief summary, the following can be said about the disadvantages of the presently used dental cement system:

Phosphate cements are harmful to the pulpa due to their strong acid reaction during setting; they are also porous and therefore offer no resistance to the penetration of micro-organisms which may cause secondary caries.

Zinc oxide-eugcnol-preparations are not harmful to the pulpa. but are highly soluble; their compressive strength is much lower than that of the phosphate cements.

Polycarboxylate cements are harmless and highly insoluble. but less compression-resistant than phosphate cements.

In all three systems the compressive strength is inadequate in view of the fact that chewing pressure is rather high.

It should be noted parenthetically that the compressive strength of other dental cements. namely the socalled silicate cements, which are used for permanent fillings, is twice as high as that of the phosphate cements. However, they are extremely harmful to the pulpa and may therefore only be used over the top of linings.

Accordingly. it is the object of this invention to provide self hardening dental cements which are not harmful to the pulpa and have high compressive strength. This and other objects will become apparent to those skilled in the art from the following detailed description.

SUMMARY OF THE INVENTION The present invention relates to dental cements and more particularly. relates to dental cements containing zinc oxide and an aqueous solution of a polymer of an unsaturated alpha. beta-dicarboxylic acid.

DESCRIPTION OF THE PREFRRED EMBODIMENTS In accordance with the present invention, a selfhardening dental cement is provided containing. the liquid component, an aqueous solution of a polymer of an unsaturated alpha. beta-dicarboxylic acid. and as the powder component. zinc oxide.

The liquid component is an aqueous solution of polymers of unsaturated alpha. beta-dicarboxylic acids.

Preferred are the polymers of unsaturated alpha. betadicarboxylic acids with four to five carbon atoms. Particularly suitable is polymaleie acid. Polyitaconic acid. as well as copolymers of the above mentioned two acids and their copolymers with other unsaturated carboxylic acids. particularly acrylic acid. can also be used. In copolymers with acrylic acid. the latter is preferably pres ent in an amount of0.l to 999% by mole. that is. in an amount of less than i0 71' by mole.

The polymeric acids and their copolymers are used in aqueous. at least 20%. solutions. ln general. a con ccntration of 65% will not be exceeded, otherwise gelling may easily set in or the solutions may become too viscous. The preferred concentration range is between 35 and 65%. particularly between 40 and 509 The solutions should be used in a viscosity of at least 0.5 poise; solutions with viscosities over 3.000 poise. as a rule over 600 poise. are generally not suitable since they are difficult to process and the stirred cements tend to form cobwebs. A preferred viscosity range is between 2 and 200 poise/25 C. particularly between 5 and l00 poise/25C.

The production of the water-soluble polymers used in this invention is known. (see eg. DOS l.9-l4.756; l.570.708; 1.645.100 as well as German Pat. No. i.lb2.083; J.L. Lang et al.: J. of Polymer Science. A l. i123 (i963); CS. Marvel et al.: J. of Organic (hemistry.24, 599(1959).

The polycarboxylic acids. particularly polymaleic acid. can be easily obtained according to known methods in solid form, for example. by further concentration of concentrated solutions in vacuum. by freeze drying, or by precipitation from aqueous solutions with nonsolvents for use in predosing of dental cements as described below.

The liquid component can contain additionally polyacrylic acid, generally used for this purpose, so that a particularly great adhesion is achieved.

The powder component is substantially the conventional zinc oxide. Naturally, the zinc oxide used must be available in a purity appropriate for medical purposes; it must be particularly free of arsenic. Since the aqueous polycarboxylic solutions generally react rapidly with zinc oxide. deactivation by heating is necessary. Preferably, the zinc oxide will be heated to relatively high temperatures. particularly between 1,200 to l.400C for several hours in order to achieve sufficiently long preparation times.

As in the case of phosphate cements. the zinc oxide need not be pure. It can contain, in known man ner. certain portions of other metal oxides. particularly magnesium oxide or bismuth oxide. but not more than 20%, preferably up to ltl /r.

Other solid substances which are substantially inert, i.e.. they do not react with the polycarboxylic acid of the liquid or only to a minor extent. can also be added to the powder. Such solid substances are, for example. aluminum oxide. calcium phosphate titanium dioxide, calcium fluoride or other flourides. which can also serve to improve the mechanical properties. to change the consistency of the stirred cement, and to achieve certain medicinal effects. Naturally, pigments, disinfectants and similar substances can also be added in known manner.

The two components, that is, the powder substantially of zinc oxide. and the polycarboxylic acid solution. are mixed in a ratio of 0.4:l to 4:] of powder to solution, depending on the consistency required by the dentist for the particular purpose. For cementing and root canal filling a relatively small powder addition will be used. while underfillings are mixed with a relatively large amount of powder. as is customary in dentistry. By varying the mixing ratio, it is also possible to vary the setting time: the more powder used. the sooner the setting will start. A preferred mixing range is a pow der/liquid mixing ratio of 1:] to 2.5:l. In general. the mechanical properties are the better the more powder is worked into the mixture.

The self-hardening compounds according to the in vention generally have a processing range otone to several minutes. and. as a rule. are hard in less than minutes.

In recent years. it has become increasingly popular to predose dental preparations in socalled shaking capsules. The liquid and powder are generally housed in two separate compartments and then combined directly before use by suitable devices. and subsequently mixed mechanically.

Predosing is also applicable to the compositions according to the invention. la a special embodiment. the usual subdivision into powder and liquid. that is. in the present case into zinc oxide and polycarboxylic acid so lution. can be replaced by a subdivision into zinc oxide. solid polycarboxylic acid. and water. This embodiment has the advantage that it permits reliable predosing and facilitates mixing. since it avoids the relatively viscous solutions. Such systems can be furthermore so varied that the solid components. that is. zinc oxide and polydicarboxylic acid. are premixed and packed as a predosed powder mixture since the solid substances do not react with each other. The weight ratio of zinc oxide to polymer can be 20:l-0.6:l, preferably l0zl-U.8:I and most preferably 5:ll.5:l or

211-6151. The second component is then water. if

necessary, with bactcriostatic additions (see DOS b90303).

The pre-mixed dental preparation according to the invention can be produced and stored in small amounts which suffice as a pre-dosed preparation. mixed with water, for immediate use at the dentist for one patient, and it can also be produced and stored as a premixed preparation of some hundred grams or more of whose bulk the dentist can take the smaller quantity which he needs. mixed with water. for the treatment of one patient.

The usual division. that is. polydicarhoxylic acid solution. on the one hand. and zinc oxide. on the other hand. is also suitable for prcdosing.

The compositions according to the invention can be used primarily in the dental sector for strengthening tooth prosthesis parts, such as inlays. crowns. bridges etc. as well as orthodontic devices. as underfilling and puloprotectives under toxic permanent fillings like silicate cements or plastic fillings based on methyl methacrylatc, as well as root fillers.

Unlike the phosphate cements. the cements acc rding to the invention are not harmful to the pulpa and til are not porous; the latter property is of great importance for avoiding secondary caries. (ompared to the zinc oxide-eugenolpreparations and the polycarboxylate cements. the cements according to the invention are characterized by a far greater compressive strength.

It could not be expected that cements containing polymaleic acid would show these properties and particularly a superior compressive strength.

Examples In the following examples the addition of pigment.

which is customary in the production of colorations resembling teeth is not specifically mentioned since it corresponds to the state of the art.

EXAMPLE l Polymaleic acid, suitable for dental purposes, and produced according to the method of DOS 1,944,756 is dissolved with water to a concentration of 51 by weight. The solution has a viscosity of l8 poise/25C.

The powder used is a mixture of a zinc oxide and magnesium oxide in a ratio of 19:1, both substances meeting the purity requirements of DAB 7. it is produced in known manner by heating to 1.3 50C. grinding and shifting through a sieve of u mesh.

When the polymaleic acid solution and the powder are mixed in a weight ratio of 1:13. we obtained a mixture that is highly suitable as a strengthening cement for dental purposes. and which hardens within a few minutes. The compressive strength tested according to the guidelines of the FDI specification (FDI Federation Dentaire Internationale) no. 6, par. 4.31; 4.3.2 and 4.3.4, is 1,210 kg/cm' EXAMPLE 2 When the components of Example l were used, but in a powder-liquid ratio of0.9: l. we obtained a cement which is particularly suitable for strengthening large tooth prosthesis parts. like multipart bridges etc. The compressive strength is, in this case. 950 kg/cm after one day. and 1,040 kg/cm after 7 days.

EXAMPLE 3 The components of Example 1 are mixed in a pow tier-liquid ratio of 3: I. We obtained a consistency which is particularly suitable for underfillings; the setting starts after about 1 /2 minutes and leads very soon to a solid product. The compressive strength. measured according to the specification of FDl is 1,350 kg/cm".

EXAMPLE 4 Polymaleic acid. produced according to DOS 1,645,100. is used as a 47 92 aqueous solution. When this solution is mixed with 1.2 parts of the powder of example I. we obtained a mixture which is suitable, inter alia. for strengthening plastic crowns.

The following longtcrm tests prove that the compressive strength of the set cement under water in creases over a long-time period.

( HIIHWLNsHU strength lllltl 3 ts ltl lll IZIU EXAMPLE 5 The solution of example 4 is used and mixed with coated aluminum. and welded. The foil bags are placed into the cover part of two-compartment containers, as are described in DOS 1.910.885. 105 mg of the powder of example 1 are filled into the container part provided zinc oxide. which is deactivated in known manner by 5 heating. This powder is yellowish and is therefore used as m'xmg Chamber without pigment addition. When the powder and liquid when F a fined n described m D are mixed in a ratio of l.5:l we obtained a strengthen- 9 usad we Obwm by mechanical! g Cement for inlays shaking device. a compound ofoptimum consistency 10 which is suitable as a strengthening cement. EX P 6 AM LE COMPARISON IESTS 70 g of the powder of example 1 are mixed with 30 In Order to Confirm h hj hc Compressive strength. g finely ground b smuth phosphate. The powder thus we made Comparison tests m cummcrcia] Prepflfflobmlned d f P g with 30 ilqlmous p ll" 5 tions of the three systems. Since the compressive maleic acid solution in a ratio of 1.6:] and used for fill- Strength depends to a m @xwnt on he n isten y "8 Tool Canal$- of the mixed cement. as mentioned above. comparison EX P E tests are only meaningful if we start in all cases from the AM 7 same consistency. in this connection, it should be mena 58 Solution of polymalek acid, produced accord tioned that the relatively high compressive strength valg to DOS 1570708 and subsfiquem hydrolysis, is ues which are indicated in some examples in DOS made into a paste with l.5 parts of the powder of examwere always achieved mlxmres where ple l and is used as a pulp protective under silicate cea relm'vely lalfge "l Of puwder was used so that ment filli the resulting v scosity was far above normal. Such preparations are difficult to process and thus undesired in EXAMPLE 8 dental practice.

In the comparative measurements. we proceeded 60 g of the powder of example I are mixed with 40 therefore strictly according to the guidelines of the FDI g aluminum oxide (particle size less than 20 [.L) and specification no. 6 regarding consistency. production made into a paste with the liquid ofexamplc l in a ratio of the test pieces. and measuring method. We therefore of 22:1. The cement thus obtained has a compressive tested compositions whose consistency meets best the Strength of 0 kg/cm requirements in dental practice.

RESULTS: Material ('ompressiie strength (kg/cm"! According to the invention. ex. l L2 It) According to the invention. ex. 4 L070 phosphate cement A 740 phosphate cement B 050 z nc oxide-eugenobpreparation C I05 Zinc oxide-eugenol-preptiration D I EBA cement *E 5 It! Polyearboxylate cement F 580 Polycarboxylate cement G 530 Commercial preparation based yinc midweugcnol. iiiiprtued li the addition ut FBA (oc'thoxybemuic acid 1. Names of the commercial products.

EXAMPLE 9 When the powder ofexample l is mixed with 3 7c caL cium fluoride. we obtained. after stirring in the liquid of example 1. a cement which is particularly suitable for orthodontic purposes.

EXAMPLE I U Polyitaconic acid. produced according to DOS 1.944.756 is used in a 54 71 aqueous solution. l.() g of the solution is stirred with 2.1 g of the powder mixture of example 8 and used as an undert'illing cement.

EXAMPLE ll The polymaleie acid solution of example 1 is filled in portions of 75 mg. into foil bags consisting ofplastic- Hxodoni Bayer Phosphavcmcnl Crowntil (rownal with fluoride Opotow EBA Durelon Pol C ecmentation The comparison tests clearly prove the superiority of the cements according to the invention.

Instead of the polydicarboxylic acids used in the examples. other polymers of unsaturated alpha. betadicarboxylic acids as well as copolymers thereof can be used. Particularly suitable are copolymers of maleic acid and itaconic acid. where the maleic acid portion is preferably relatively high. for example, by mole. Suitable are also copolymers of unsaturated alpha. betadicarboxylic acids with unsaturated monocarhoie ylic acids. particularly acrylic acid or methacrylic acid. Here too. copolymers with a relatively high content of dicarboxylic acid units deserve preference. for example, copolymers which contain primarily maleic acid. in addition to acrylic acid or methacrylic acid. particularly copolymers which contain more than 90 "4 by mole maleic acid.

Also suitable are polymers or copolymers of the above mentioned type which additionally contain small quantities. that is. not more than 10% by mole. of

monomers that are free ofcarhoxyl groups. Particularly suitable are copolymcrs with methacrylic esters, acrylic amide, methacrylic amide. as well as their derivatives substituted on nitrogen.

For the following examples known methods were applied to obtain polymers in solid form. eg by precipitating from a concentrated aqueous solution with solvents miscible with water. by drying aqueous solutions in a thin layeri preferably in the presence of drying agents, or on cylinder drying machines by applying external heat. Also. by free7cdrying from aqueous solu tions. these polymers can be obtained as dry powders.

Afterwards the polymers are finely divided; during this manipulation there can be added favorably antiblocking agents in small quantities. as e.g. metal stearates. especially zinc stearate. or highly dispersed silica.

in the following examples the addition of one or more pigments and other usual additives which are customary in the production of dental cements is not specifi call mentioned since it corresponds to the state of the Lift.

EXAMPLE 1 ltltl g of solid polymaleic acid are mixed with 28.0 g desactivated zinc oxide and 2 g Aerosil (highly dispersed silica). in order to get a strengthening cement for gold inlays 0.38 g of this powder mixture are spatu lated with 0.11 g water. The mixture hardcns after a few minutes; the compressive strength of this cement is 1.020 kg/cm after 24 hours.

EXAMPLE 2 For making a cement to protect the pulp, a powder mixture of 100 g polymaleic acid and 400 g desactivated zinc oxide is made. g of this mixture are spatulated with (H g water. Thus we obtain a quickly hardening dental cement which is suited for cavity linings under self-hardening dental filling materials on methyl methacrylate basis.

EXAMPLE 3 The powder mixture of Example 2 is filled. in portions of each 41H) mg. in the mixing chamber of two compartment containers as are described in DOS i 9ltl.885. Furthermore the capsules contain in the cover part 85 mg water each being stored in foil bags of plastic coated aluminum. When such a filled Capsule is used, as described in DOS 1.910.885, we obtain by means of a mechanical shaking device, a cement of optimum consistency for cavity linings.

EXAMPLE 4 F-lt) g desactivated Zinc oxide, containing 5 "/r by weight of magnesium oxide and .7? by weight of alu minum oxide. are mixed with Hill g finely ground polyitaconic acid. When this powder is mixed with water in a weight ratio of 41l. a strengthening cement is obtained, the compressive strength of which is 930 kglcm after 24 hours.

EXAMPLE 5 The following components are mixed:

g polymaleic acid. 20 g polyacrylic acid, Zlltl g sintered line oxide and I g zinc stearate.

By adding one part of water to 3.2 parts of the above mentioned powder. we obtain a mixture which is Well suitable as a strengthening cement for crowns and bridges.

EXAMPLE 6 For use in capsules in predosed quantities the powder mixture of Example 5 is filled in portions of 320 mg into the capsules mentioned in Example 3. which also contain 1 10 mg water in foil bags. By means of a mechanical shaking device we obtain a cement of similar consistency to that one described in Example 5.

EXAMPLE 7 50 g of a copolymer, which contains 94 mol .7? maleic acid and h mol It methacrylic acid dimethylarnide, are mixed with lfit) g desactivated zinc oxide and filled in capsules, in portions of each 450 mg,

The cover part of the capsule contains foil bags with mg water each to which (1.5 by weight of Dehydol are added as a wetting agent. By mixing these components mechanically, we obtain a quickly hardening strengthening cement.

Various changes and modifications can be made in the product of this invention without departing from the spirit and scope thereof. The various embodiments set forth herein were intended to further illustrate the invention but were not intended to limit it.

We claim.

1. A premixed dental preparation for the preparation of a self-hardening composition when mixed with water consisting essentially of zinc oxide and a polymer of an unsaturated alpha. beta-dicarboxylic acid selected from the group consisting of homopolymers of unsaturated alpha, beta-dicarboxylic acids of four to five carbon atoms and copolymers of said acids with each other and with less than H) mol percent of an unsaturated monocarboxylic acid. aerylamide, methacrylic ester or methacrylic amide wherein the weight ratio of zinc oxide to said polymer is 201] to ().6:l.

2. The preniixcd preparation of claim 1 wherein the polymer is polynialeic acid.

3. The premixed preparation of claim 1 wherein the polymer is polyitaconic acid.

4. The premixed preparation of claim I additionally containing polyacrylic acid.

5. The pre-rnixed preparation of claim 1 wherein said ratio is 0,811 to [011.

6. The premixed preparation of claim I wherein the weight ratio of zinc oxide to polymer is 5:l to 1.5:].

7. The pro-mixed preparation ofclaim I wherein said ratio is 2:1 to 6.25:]. 

1. A PRE-MIXED DENTAL PREPARATION FOR THE PREPARATION OF A SELF-HARDENING COMPOSITION WHEN MIXED WITH WATER CONSISTING ESSENTIALLY OF ZINC OXIDE AND A POLYMER OF AN UNSATURATED ALPHA, BETA-DICARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYMERS OF UNSATURATED ALPHA, BETA-DICARBOXYLIC ACIDS OF FOUR TO FIVE CARBON ATOMS AND COPOLYMERS OF SAID ACIDS WITH EACH OTHER AND WITH LESS THAN 10 MOL PERCENT OF AN UNSATURATED MONOCARBOXYLIC ACID, ACRYLAMIDE, METHYACYLIC ESTER OR METHACRYLIC AMIDE WHEREIN THE WEIGHT RATIO OF ZINC OXIDE TO SAID POLYMER IS 20:1 TO 0.6:1.
 2. The pre-mixed preparation of claim 1 wherein the polymer is polymaleic acid.
 3. The pre-mixed preparation of claim 1 wherein the polymer is polyitaconic acid.
 4. The pre-mixed preparation of claim 1 additionally containing polyacrylic acid.
 5. The pre-mixed prEparation of claim 1 wherein said ratio is 0.8:1 to 10:1.
 6. The pre-mixed preparation of claim 1 wherein the weight ratio of zinc oxide to polymer is 5:1 to 1.5:1.
 7. The pre-mixed preparation of claim 1 wherein said ratio is 2: 1 to 6.25:1. 